The present invention relates in general to towed marine acoustical cable systems, such for example as marine seismic streamers of the type having a plurality of serially connected streamer sections each formed of a buoyant fluid filled plastic tube containing stress members, structural spacers, and optionally containing a hydrophone array and/or other seismic prospecting components, adapted to be towed at a pre-determined depth for purposes such as seismic surveying or prospecting or other underwater acoustical detection applications. More particularly, the present invention relates to coupler devices for serially connecting together each of a successive pair of serially arranged acoustical streamer sections to provide reliable couplings having sufficient axial strength to withstand strains imposed by a long acoustical underwater streamer of several thousand feet and providing effective sealing of plug cavities at the connection sites so that the electrical connections are effectively isolated from the surrounding water.
Heretofore, a number of marine seismic detection cables or streamers, the terms being used interchangeably, have been devised for making seismic surveys of terrestrial subsurface structures disposed beneath the surface of seawater. In general, the marine seismic streamers have included a leading cable and a plurality of serially connected active sections formed of a buoyant fluid filled plastic tube surrounding an array of hydrophones, strain cables, structural spacers, transformers, and mechanical and electrical connectors such as, for example, the type disclosed in U.S. Pat. No. 2,465,696 issued Mar. 29, 1949 to Leroy C. Pasley or U.S. Pat. No. 3,371,739 issued Mar. 5, 1968 to Raymond H. Pearson, and U.S. Pat No. 3,812,455 issued Mar. 21, 1974 to Raymond H. Pearson. Inactive streamer sections are also often interspersed in the string of serially connected seismic streamer sections at various locations. Such marine seismic streamers or cables may in many cases result in cables of a mile or more in length, a typical streamer system being about 7,000 feet long, with each streamer section being typically 100 feet or more in length.
During seismic survey or prospecting operations, the streamer is towed at a selected depth below the surface of the sea by a seismic survey vessel and may include any of several conventional devices for maintaining the seismic cable at the desired underwater depth. The cables are sometimes provided with a plurality of weights at spaced intervals to make them negatively buoyant and flotation means or rigid boom means may be associated with the cable to assist in maintaining it at the desired depth. Alternatively, regulation of the buoyancy of the streamer may be achieved by pumping oil or other buoyant fluid into or withdrawing such fluid from the streamer sections to maintain a pre-determined degree of buoyancy, or, as another option, the steamer may be positively buoyant and paravane type structures may be used employing diving planes which are regulated in preselected relation to pressure responsive devices to maintain the streamer at the desired depth.
Because of their operation at various subsurface levels, the streamer sections may occasionally strike ocean bottom reefs, shell-beds or other submerged objects, damaging the connections between successive sections and permitting saltwater contact with electrical conductors in the system resulting in electrical leakage and/or shorting. Similar damage may occur to the plastic sleeve or boot portion of one or more streamer sections, necessitating removal of that section of the streamer to allow replacement or on-deck repair of the damaged section. If the electrical connections are damaged by seawater, they must be removed and cleaned again requiring decoupling of the involved streamer section from the remainder of the streamer and subsequent reconnection of the repaired section with the remaining streamer sections.
Also, the strain cables running through each of the streamer sections must be connected together at the junctures between successive sections in such a way as to provide a strong mechanical connection lending great axial strength to the system, so that streamer sections near the upstream end of the streamer are capable of withstanding the strain imposed by all of the succeeding sections. Also, the configuration of many prior art connections between successive streamer sections have been such as to create turbulence in the surrounding seawater, thus producing a poor signal-to-noise ratio. Furthermore, many of the prior art connections or couplings do not effectively resist relative rotation between adjacent successive streamer sections because the connector components are rotated relative to each other during assembly and are not adequately restrained against rotation during use.
An earlier seismic streamer connector structure effectively eliminating or minimizing many of these problems is disclosed in U.S. Pat. No. 3,812,455 issued to Raymond H. Pearson. However, improvements over that structure have been sought by the assignee of the present application, who is also the assignee of that patent, to provide improved distribution of tensile stresses so that the walls of the stress carrying outer housing portions may be thinner and therefore reduce the weight of the connector joint, and by separating the sealing/electrical connecting parts of the coupling from the stress-carrying parts so that the sealing/electrical connecting portions, in effect, float in the stress-carrying portions to avoid transmittal therebetween of deformations of the stress-carrying portions.
An object of the present invention, therefore, is the provision of a novel connector structure for connecting together successive sections of serially connected marine acoustic steamers, to provide adequate axial strength to withstand the strains imposed by a long series of succeeding cable sections trailing behind the connection, and effectively separating the stress-carrying components to avoid transmittal to the latter of deformations of the stress-carrying parts.
Another object of the present invention is the provision of a novel connector structure for successive sections of marine acoustic streamers formed of a plurality of serially connected sections, wherein the coupling components to be mated together are connected without relative rotation between them so that relative rotation between interconnected mating sections of successive streamer sections is eliminated, and which improves the distribution of tensile stresses so as to permit use of thinner walls of the stress-carrying outer housing portions.
Another object of the present invention is the provision of a novel connector structure for intercoupling the successive sections of a marine acoustic streamer formed of serially connected sections, wherein plug cavities are provided for interconnecting electrical plugs to electrically coupled successive sections together upon mating of complimentary semi-cylindrical coupler components, and wherein highly reliable sealing and electrical connecting components are disposed in floating relation in the stress-carrying components deformations are not transmitted to the sealing and electrical connecting parts.
Yet another object of the present invention is the provision of a novel connector structure for interconnecting successive sections of a marine acoustic streamer as described in the preceeding paragraphs, having a novel construction which greatly facilitates field servicing of the streamer sections by having the electrical terminations on the streamer sections readily accessible, and more particularly by providing for easy access to the wired side of the insulator panels, to facilitate rewiring, troubleshooting, and permit incorporation of spare conductors, and wherein the pins and sockets in the insulator panels are sealed to prevent fluid lost or migration but which can be readily removed, replaced and resealed in the field.
Another object of the present invention is the provision of a novel connector structure for interconnecting successive sections of a marine acoustic streamer, wherein the stress members, for example three wire rope members, are anchored in a swanged terminal retainer at each end of each streamer section wherein the retainer is of insulating material or is coated with insulation to provide electrical isolation of the stress members so that the stress members are electrically "floating" rather than having to be electrically grounded.
Still another object of the present invention is the provision of a novel connector structure for interconnecting successive sections of a marine acoustic streamer, wherein a large number of electrical pin and socket connections are provided for interconnecting various signal wires between the acoustic transducers and the towing vessel, and wherein plug and socket connectors and housing facilities are provided for a program plug to provide for programming or selective interconnecting of various signalling connectors that are not part of the acoustic signalling conductor system and for selectively varying interconnections or groupings as desired between the acoustic signalling conductors without requiring jumper rewiring of wires or conductors in the connectors.
Other objects, advantages and capabilites of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.